Assaying the estrogenicity of phytoestrogens in cells of different estrogen sensitive tissues

There is currently much concern that a wide range of both synthetic and nat urally occuring enviromental chemicals may act as endocrine disruptors (ED) , and may adversely affect humans and wildlife. We examined the estrogenic effects of the phytoestrogens daidzein (DAI), equol (EQU) and O-desmethylan golensin (O-DMA), two metabolites of DAI, in three different assays. Bindin g affinity to the estrogen receptor alpha was 1000-10,000-fold lower compar ed with the endogenous estrogen estradiol. In the receptor positive cell li ne MCF-7 the phytoestrogens induced the expression of a reporter gene. The E-SCREEN is based on the estrogen-receptor binding induced proliferation of the human breast cancer cell line MCF-7. We also adapted the E-SCREEN for the estrogen-receptor positive human ovarian cancer cell line BG-1. The tes ted phytoestrogens induced cell proliferation in both cell lines, but not i n the receptor negative human breast cancer cell line MDA-MB-231. The phyto estrogen-induced cell proliferation could be blocked by addition of the rec eptor antagonist 4-hydroxytamoxifen (OHT). Combination treatments with the endogenous estrogen estradiol showed competitive effects in MCF-7 cells. Th ese studies demonstrated that the tested phytoestrogens exerted estrogenic responses in cells derived from two different tissues, breast and ovary. Fu rthermore, we demonstrated that BG-1 cells are a suitable additional cell s ystem to investigate estrogenicity of test compounds. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.